Will eating some fat before Z2 rides help fat oxidation during?

I know there’s a big push to fuel our workouts and much of that focus is on carbohydrate. I’ve just started TB MV1 this week and some of my goals include weight loss through a modest calorie deficit and improving fat oxidation on longer rides. I did some gas exchange testing pre-COVID and I’m pretty bad at using fat much above 150w which just about the lower limit of my Z2.

I know I have plenty stored fat (lol) but would eating some before aerobic rides possibly help improve fat oxidation? I can do 90-120mins z2 fasted generally but don’t like being hangry. I can comfortably eat eggs and some avocado, for example, pretty close to the beginning of a ride with no gastrointestinal issues. Any thoughts? Thanks!!

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I can’t offer much in the way of true science here but this is what I’ve learnt from reading and experimenting myself:

  1. as you’ve alluded to, what fuel source you use (at least in the short term) is more about intensity of the workout than how much of a certain fuel you have stored. If this wasn’t the case, bonking wouldn’t exist

  2. having said that, you can train your body to use fat a little bit better. But I think the approach to becoming more “fat adapted” is a long term and multi-pronged one. It involves limiting carbohydrate over months or years, and probably limiting the intensity of your workouts for a while at the beginning of this process, so that you don’t shock your body too much by the sudden change.

  3. If weight loss is your primary goal, then a calorie defecit should be your primary goal. Not the ONLY goal, but definitely the main one. If you focus too much on fat intake/burning but eat a calorie surplus that mainly consists of sugar, you’re still likely to gain weight.

  4. I tried the keto diet (basically very very low carb). I found it didn’t partner well with cycling intensity any higher than zone 2. If I was an endurance cyclist with no interest in hard efforts, I could’ve happily continued, but low carb doesnt work well with most TR workouts because of the intensity.

  5. Sounds like you are already aware of the carb-centric focus that the TR podcast has. I think they’re right, they have a sensible approach. A long term one. I’ve tried it myself and find that consistency in training and eating well is a much better way to live and ride than any kind of faddy lifestyle change such as keto or fasting etc (although these can be useful tools if used sensibly).


See some other topics here related to weight loss and fat burning


Best practices from what I’ve read:

  • you can chase a marginal gain by doing the first 45-60 minutes fasted and then start eating on the bike
  • only do that a maximum of twice a week

Your body can’t really tell the difference between fat from foods and fat mobilized from your body’s stores, so it’s not going to have any effect on your fuel use.

It might help keep you from feeling hangry, though, so if your GI system can handle it, why not?


General comment: all of the focus on becoming “fat adapted”, fasted training, etc., is completely misguided. Even the muscles of an untrained person are very good at using fat, at least at rest - the trick is convince them to keep doing so during exercise. The primary way you do that is to minimize the shift to carbohydrate, by having lots of mitochondria, capillaries, etc.

IOW, training isn’t really about increasing fat utilization, it’s about decreasing carbohydrate utilization.


and the simple and pragmatic ways to do that are:

  • not eating sugar/carbs before you ride
  • keep force production low while on the ride

I don’t know of any evidence that the former makes any difference in the long run. Even training all the time when glycogen depleted doesn’t really seem to pay performance benefits.

As for the latter, you can of course minimize carbohydrate use during a given workout by going easy… but that doesn’t really get anywhere, i.e., you get better by doing more, not less, than what you’re used to.

Eat lots of carbs, ride hard, rinse, repeat.


@old_but_not_dead_yet has it right as far as I understand. Fat utilization is more a function of how much aerobic headroom you have rather than what your diet is. It all ends up going through the same chain at the end to turn into energy so it just comes down to do you have enough headroom for your body to faff about getting energy out of fat or not. If you do it does, if you don’t it fills with glycogen. If you run out of glycogen your work rate just gets clamped to what you can do off of fat alone… also known as bonking. Working at a higher intensity that is still in your aerobic zone for as long as is manageable is the ‘best’ way to increase your rate of fat oxidation during exertion.

But I’m not an expert, just a monkey on a bike.

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How do you determine this?

To do it ‘perfect’ you go get lab tested. In reality just ride hard enough that your breath starts to elevate a little above ‘recovery’ then hold that for 3+ hours. It’s ‘good enough’.


FYPFY :slight_smile:

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Lab tests are a waste of time, money, and energy.


Rock on :metal:t3:


My lab tests (and waistline) showed I’m not an effective fat burner :sweat_smile:

Admittedly I don’t have a background in sports science, but I’d venture any gains to be had here are marginal, and there’s a chance of counter-productivity.

Fuel your workouts properly, and that will lead to the best performance. Better performance = better adaptations, and more calories burned.

If you’re looking to lose weight, reduce food and carbohydrate intake away from the training. Track your intake (myfitnesspal is a quick and easy method) and adjust as needed. Unless you are very overweight (in which case, performance probably isn’t priority number 1), beware of dropping too much weight/dropping calories too quickly - your performance will plummet.

Otherwise, train the system you’re looking to adapt, and eat enough to fuel the training and facilitate adaptation. Train-eat-sleep-repeat.

Plenty of people got very, very fast in years gone by using this method.

I don’t think you can make yourself a better fat burner - your body is a hybrid already and will dip into the most appropriate fuel sources for the intensity of work you are doing based on what it has available.
As others have said fuel up and ride. :grin:

I’ve always found this a very “approachable” article for the layman.

Not mentioned specifially in the text but yes, there is some evidence that pre-exercise fat increases fat oxidation. But in the overall picture it does not appear to be very significant for project weight loss.

Volume is king!


Good thread and one I am very much interested in right now. I had a body scan 4 weeks ago, from memory I was around 88kg with 25% body fat with a recommendation to lose half of that, so an 11kg mass loss from fat (in an ideal world).

Points to keep in mind

  1. TrainerRoad focuses on performance…end of
  2. For performance gains you need to fuel your hard workouts
  3. It’s probably counter productive to become a better “fat burner”…go too far with this and your body becomes less efficient at using carbs and when you come to race you will suffer
  4. The focus for fat loss has to be about a lot of your kj expenditure coming from fat. You can ride fasted for 2 hours.

There are some very good podcasts around at the moment, Fast Talk episode 123 with Dr Brian Carson from Limerick University. He specialises in the physiology of carbs, I’ve listed to this over and over and there are some very good take aways in it. One being that after 2 hours fasted if you then start to use say 25g of carb per hour for a further 2 hours your body will continue to utilise fat in the same way as it did for the first 2 hours thus extending the fat burn and your ability to ride for a further 2 hours with too much suffering.

My intention is to utilise multiple tools to attack my personal goal

  1. Maintain high intensity sessions and fuel for them appropriately
  2. Continue with resistance training
  3. Do long rides with the first few hours fasted

My primary focus right now is health related not performance related.

Other podcasts of note

That Triathlon show episode 252
Inside The Big Ring episode 88

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This is very interesting thank you!!!